Planet 5 min
Global warming: plastics cool things down
Tackling global warming is the challenge that humanity must take on as soon as possible to prevent the problem from getting out of hand. It is no longer time for debate; it is time for action. Fortunately, solutions, some of which are based on the properties of polymers, are emerging.
Global warming: plastics cool things down
Global warming: plastics cool things down

Plastics cause the planet to reflect

Scientists are now unanimous in their belief that global warming is largely due to man. Since the first industrial revolution, we have constantly increased our emissions of greenhouse gases such as methane and many more besides, such as CO2. These gases stagnate in the atmosphere and form a barrier that prevents heat from escaping properly into space. The planet heats up and the climate goes haywire. In order to cool the Earth, we must therefore succeed in making it easier for heat to leave our atmosphere
The first solution involves emitting less CO2, the second involves 'helping' the planet to cool down, and the third involves capturing and eliminating the gas.

The albedo* effect, plastics radiate

For the past ten years or so, the same ritual has been performed every late spring. Dozens of mountaineers deploy huge white tarpaulins made of polyester and polypropylene, ultra-resistant polymers, on various Alpine glaciers in Switzerland, where it all began, but also in Italy, Austria, France and Germany. They have a dual role: to insulate the snow layer from the summer heat and to improve the reflection of ultraviolet rays in order to stop the ice from melting. This technique has proven its effectiveness, as various studies estimate that it has reduced local snowmelt by 50 to 70%. This is good, but these same studies emphasise that this figure is insufficient in relation to the volume of ice that melts each year, particularly at the poles.

 

Tens of square metres of tarpaulins made of polyester and polypropylene are spread over Alpine glaciers every year to insulate them from the heat and improve the reflection of sunlight.

Pack ice is also affected by melting ice, but global warming is not the only cause. Pack ice is becoming darker because of the deposits left by clouds of soot from coal-fired power stations in particular. It is well known that darker surfaces tend to absorb heat rather than disperse it, thus contributing to global warming. On the other hand, the lighter the surface, the more solar radiation is reflected back into space. This is known as the albedo effect. Scientists must keep a close eye on this phenomenon. When pack ice melts, it uncovers the ground or the oceans, which reflect a smaller proportion of the sun's rays and thus contribute to the ice melting more quickly. A real vicious circle.

* Albedo is the reflective power of a material or surface. It is expressed as a percentage: 0% meaning that all light is absorbed and 100% that all light is reflected. Its value is noted with a number ranging from 0 to 1. The average albedo of our planet is 0.3, but there are wide variations, with snow having an average value of 0.8 and the oceans having an average value of 0.07.

Polymers chill pack ice

The Albedo effect is a promising avenue for geoengineering. Far from giving up, some researchers are proposing to pump sea water and spray it onto the pack ice as soon as the temperature is close to 0°. It's a bit like the principle of snow cannons in ski resorts. Not too complicated, then... except that in this case, the water has to be desalinated first because, as everyone knows, salt and ice do not mix. This is a feasible operation, but it still requires a lot of electrical energy for a very average yield. However, 're-icing' the pack ice would require millions of m3 of water and therefore hundreds of thousands of kWh! Nevertheless, science is making progress in the field of membranes designed to filter sea water.

 

Regulating the ice pack using snow cannons could be possible, thanks particularly to the combined effect of high-performance polymer membranes and polymer photovoltaic cells.

American company NanoH2O has developed a new polysulfone polymer membrane whose pore size is very close to that of a water molecule (around one nanometre). When the pore size of the membrane is equivalent to the size of the water molecules, the latter connect to each other to form a kind of thread, which makes it possible to accelerate the flow without increasing the amount of energy required.

In other words, these new generations of membranes allow for a much higher efficiency. This technology could be combined with that of French company Mascara, which has developed an autonomous desalination plant that operates using polymeric photovoltaic cells. The first tests are very conclusive. Admittedly, this mini-factory was installed in Saudi Arabia, but the sun is also present at the poles, particularly in the off-season when temperatures are already cold enough to operate snow cannons.

Plastics know a thing or two about rays

Other companies have come up with the idea of designing floating solar panels. The photovoltaic panels are fitted onto a modular frame made of high-density polyethylene (HDPE), which can be assembled much like a construction set. It is thus possible to cover more or less large areas.

The idea is to install them primarily on artificial reservoirs (irrigation basins, drinking water reservoirs, aquaculture ponds, quarry lakes) so as not to disturb nature. Their primary function is to produce green electricity, but that is only one facet of their effect. The albedo of a solar panel is much higher than that of a body of water, which is often close to black. It is certainly only a drop in the ocean, but is it not from small rivers that great rivers are made?

 

Floating solar panels installed on a plastic frame also have a significant effect on the reflection of solar radiation.

Wrapping up on the albedo effect, a 2012 study by the Canadian University of Concordia estimated that increasing the albedo value of cities by 0.1 would make it possible to avoid the emission of 130 to 150 billion tonnes of CO2 for 50 years. This is no mean feat given that global CO2 emissions approach 40 billion tonnes per year. Creating this real thermal shield requires painting your roof not with ordinary paint, but rather with a so-called thermal paint. By increasing the reflection of the sun's rays, the thermal paint prevents buildings from storing heat in summer and therefore limits the need for air conditioning.

 

PVDF-based paints or polyolefin films allow roofs to achieve an albedo coefficient approaching the maximum possible.

These paints are enriched with polymers such as polyvinylidene fluoride (PVDF) latex developed by Arkema. This polymer gives the paints a near-perfect whiteness and allows the roofs to have an albedo coefficient close to 1. This is the coating that can now be found on the roof of the Wimbledon centre court, the Pearl Tower in Shanghai, the Renaissance Center in Detroit, and on many buildings and skyscrapers around the world. Others, such as Amsterdam Airport, have chosen to install thermoplastic polyolefin films on all their roofs. This is a recyclable material that requires no maintenance and can remain in place for up to 50 years. In addition, it is highly resistant to chemical aggression, such as that caused by paraffin, which is very present in its vapour form in airports.  Like PVDF-based paint, its whiteness allows it to effectively reflect sunlight back into space, which is one of its top priorities.


Find below the articles of Plastics le Mag on the same topics:
A reflective polymer coating for staying cool
Thin insulation
A giant blanket to keep a glacier cool!
Solar power stations floating on water

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